The present invention relates to expansion valves of the type responsive to a thermally generated fluid pressure signal for controlling flow through the valve and is particularly suitable for controlling flow of refrigerant from the condenser to the evaporator in a refrigeration or air conditioning system. In particular, in automotive air conditioning systems it has been found desirable in certain vehicle installations to utilize a valve having a right angle configuration between the inlet and the outlet for facilitating installation in the system conduits.
A known right angle expansion valve arrangement for controlling refrigerant flow employs a fluid pressure capsule which has a pressure responsive diaphragm therein and which is attached to the valve block with a capillary tube communicating a fluid pressure signal from a thermal sensor to one side of the diaphragm. The opposite side of the diaphragm has a pad or plate registered thereagainst for contacting a plurality of push rods which, in response to the integrated force of the pressure acting on the diaphragm, are operable to effect movement of a moveable valve member for controlling flow from the valve inlet to the outlet. One known configuration for such a valve is shown in FIG. 2 where the valve body 1 has an inlet fitting 2 which has a passage 3 therein which communicates with a valving passage 4 which has a valve seat 5 with a valve member in the form of ball 6 seated thereagainst for controlling flow to an outlet passage 7 in an outlet fitting 8 which is disposed at generally right angles to the fitting 2. The valve member is retained against the valve seat 5 by a retainer 9 which is biased in the direction to seat the check ball by one end of a coil spring 10 which has its opposite end retained by a ring 11 which is threaded into the passage 7 for adjusting the spring preload on the member 9.
A plurality of push rods, one of which is shown and denoted by reference numeral 12, are disposed about the passage 4 with the lower end of each push rod contacting the retainer 9. The upper end of each push rod is registered against a pad or plate 13 which is moved by a pressure responsive diaphragm 14 which is sealed by weldment about its periphery in the capsule 15. The capsule is connected to a capillary tube 16 for receiving a thermally generated fluid pressure signal therethrough which varies the pressure in chamber 17 as applied to the upper surface of diaphragm 14 for controlling movement of the push rods 12. A pressure equalization passage shown in dashed outline and denoted by reference numeral 18 provides pressure equalization from the outlet passage 7 to the undersurface of the diaphragm 14.
In certain refrigeration applications having a relatively high pressure drop across the evaporator, for example, a pressure drop of seventy psi (483 KPa) it has been found desirable to employ an externally equalized expansion valve where the underside of the pressure responsive diaphragm is connected through a passage in the valve block to an external capillary connected to the evaporator outlet. This has been accomplished by rerouting passage 18 to connect with an external pressure equalization passage denoted by reference numeral 19.
Heretofore, the known valve of FIG. 2 has been fabricated with the body 1 formed of brass material with the pad 13, diaphragm and push rods 12 formed as separate pieces; as, are the valve member 6 and retainer 9. The valve of FIG. 2 has the disadvantage of relatively high manufacturing costs in high volume mass production as is required for automotive air conditioning applications. Thus, it has been desired to find a way or means of improving the construction and reducing the manufacturing costs of the known right angle refrigerant expansion valves.